In "It's a Wonderful Life", Mary's wish kills George's father.

Later in the movie we learn Mary wished she could marry George. In order for this to happen, George had to stay in Bedford Falls. The only way to keep George from going to college was to have him take over the Building & Loan, which meant his father had to be out of the picture. Considering the timing, George's father probably had his stroke right around the moment of Mary's wish. Obviously, her intent wasn't to kill, but it was a necessary byproduct of the wish.